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A
AndrewBond4-Participant
4-Participant
March 16, 2023
Question

How to control precision of explicit, ALL symbolic?

  • March 16, 2023
  • 1 reply
  • 4732 views

I am trying to display the results of a calculation using MathCAD PRIME 8's symbolics feature "explicit, ALL"

 

The results are shown accurate to with 14 decimal places - which is way too precis for my purposes. I have been unable to fina a way to contol the precision of this display - Math Formatting appears to apply only to the final result.

 

I attach two screenshots, one showing what I currently get from MathCAD and the other showing what I want.

 

Does anyone know how to achieve this?

 

Thanks in advance!

 

Andrew

1 reply

W
Werner_E25-Diamond I
25-Diamond I
March 16, 2023

You may try to add the "float,n" modifier where "n" is the number of significant digits to use. But you have to keep in mind that "float" does not only modifies the display of the result but affects the precision of the whole calculation. So you should use it with care.

    A
    AndrewBond4-ParticipantAuthor
    4-Participant
    March 16, 2023

    Thanks for your reply. However, I can't seem to get that to work (see screenshot).

     

    float,2 changes the result of the variable in the display but does not seem to change its value going forward to later calcuations. So, NRd in my examples is still 2505.5134072697656 when I expand using explixit, ALL

     

    Do you have an example showing how you have used float, 2 and explicit, ALL successfully?

    W
    Werner_E25-Diamond I
    25-Diamond I
    March 16, 2023

    It would always be better to attach a worksheet for us to play with rater than posting just a picture

     

    You would have to use the float modifier in every evaluation where you want to see a certain number of significant digits.

    Your first expression just evaluates and displays N.Rd but to change the variable you would have to redefine it.

    Werner_E_0-1678976571204.png

    But if this is what you want, I would rather suggest using the "round" function

    Werner_E_1-1678976625081.png

     

    Unfortunately it seems that the combination of "float" and "explicit" does not work as desired because "float" seems to overrule "expicit" and just the result is displayed

    Werner_E_2-1678976772258.png

    So of course you may redefine your variables using "round", but this can have significant impact on the accuracy of all your further calculations which make use of these variables:

    Werner_E_3-1678976881857.png

    BTW, the inline evaluation (= display of result) after round ist mandatory, otherwise you get

    Werner_E_5-1678977007294.png

     

    Fazit: There seems to be no easy way to display in low precision the values a variable was calculated with while at the same time preserving the precision of the calculation.

     

     

     

     

     

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